So what happens to players who can't do the "Hard" stuff now when even harder stuff comes out? I'm pretty sure they're trying to get away from excluding a huge part of the playerbase, which is one reason they added Hard Mode to all the Raids and Dungeons. Players who can't do the hard stuff can still see the content, and the players who can get better rewards.
Also, Starcraft 2 and Diablo 3 have their own teams. None of them work on more than one game. (Plus their unannounced game(s)).